Human Health Critena - Methylmercury

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For general questions about the criterion. contact Mary Manibusan, USEPA, Health
and Ecological Criteria Division, (Mail Code 4304), Office of Science and
Technology, 1200 Pennsylvania Avenue, NW, Washington, DC 20460, (202)
260-3688, fax (202) 260-1036, e-mail manibusan mary@epa gov.

For specific issues about mercury bioaccumulation , contact. Erik Winchester,
Health and Ecological Criteria Division, (Mail Code 4304), Office of Science and
Technology, 1200 Pennsylvania Avenue, NW, Washington, DC 20460, (202)
260-6107

For questions about implementing the criterion contact William Morrow, USEPA,
Standards and Health Protection Division, (Mail Code 4305), Office of Science and
Technology, 1200 Pennsylvania Avenue, NW, Washington, DC 20460, (202)
260-3657

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Revised Wednesday, January 03, 2001 17.04.54
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Office of Water FacT Snape MUS

United States Office of Water EPA-823-F-01-001
Environmental Protection 4304 January 2001
Agency

Water Quality Criterion for the Protection of Human
Health: Methylmercury

Summary

The U.S. Environmental Protection Agency (EPA) is announcing the availability of a
recommended fish tissue residue criterion for methylmercury to protect human
health. This water quality criterion describes the maximum advisable concentration
of methylmercury in freshwater and estuarine fish and shellfish tissue to protect
consumers of fish and shellfish among the general population. EPA expects the
criterion recommendation to be used as guidance by States, authorized Tribes, and
EPA in establishing or updating water quality standards for waters of the United
States and in issuing fish and shellfish consumption advisories. Because consumption
of contaminated fish and shellfish is the primary route of human exposure to
methylmercury, EPA is expressing this water quality criterion as a fish and shellfish
tissue value rather than as a water column value. EPA is providing suggested
approaches for relating this criterion to water column concentrations; and also plans
to develop more detailed guidance to help water quality managers implement the
methylmercury criterion in water pollution control programs.

What are human health water quality criteria?

Human health water quality criteria are numeric values we believe will protect human
health for pollutant concentrations in aquatic media, such as ambient waters and
edible tissue EPA publishes water quality criteria under the authority of Section
304(a) of the Clean Water Act (CWA) based solely on data and scientific judgments
about the relationship between pollutant concentrations and environmental and
human health effects CWA Section 303(c) and its implementing regulations require
states and authorized tribes to adopt water quality criteria to protect designated uses
in their water quality standards EPA’s recommended section 304(a) water quality
criteria may guide States and authorized Tribes in establishing water quality
standards The resulting standards may serve as a basis for controlling discharges or
releases of pollutants EPA’s recommended human health water quality criteria are
not regulations themselves, and do not do not impose legally binding requirements.
EPA may change the section 304(a) water quality criteria in the future.

How does mercury accumulate in fish and shellfish?


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Mercury is found in the environment as a result of natural and human activities. The
amount of mercury that cycles in the environment has increased since the industrial
age. The main source of mercury is air emissions from power generation and other
industrial and waste disposal activities. During its movement among the atmosphere,
land, and water, mercury undergoes a series of complex chemical transformations
One of the products of these transformations is an organic form called
methylmercury. Methylmercury is easily absorbed into the living tissue of aquatic
organisms and is not easily eliminated Therefore, it accumulates in predators The
degree to which mercury is transformed into methylmercury and transferred up the
food chain through bioaccumulation depends on many site-specific factors (such as
water chemistry and the complexity of the food web) through processes that are not
completely understood

What adverse effects on human health are related to mercury?

Methylmercury is highly toxic to mammals, including people, and causes a number of
adverse effects Health studies and information showing neurotoxicity, particularly in
developing organisms, are most abundant. The brain is the most sensitive organ for
which suitable data are available to quantify a dose-response relationship. A recent
study by the National Academy of Science concluded that the population at highest
tisk is the children of women who consume large amounts of fish and seafood during
pregnancy, and that the risk to that population is likely to be sufficient to result in an
increase in the number of children who have to struggle to keep up in school and
who might require remedial classes or special education.

What actions reduce health risks?

States, Tribes, and Territories have primary responsibility for protecting their
residents from the risks of eating contaminated noncommercially-caught fish and
wildlife. They do this by issuing fish consumption advisories for the general
population (including recreational and subsistence fishers) and for sensitive
subpopulations (such as pregnant women, nursing mothers, and children) These
advisories inform the public that unacceptable concentrations of chemical
contaminants have been found in local fish and wildlife. They also recommend
limiting or avoiding consumption of certain fish and wildlife species from specific
waterbodies or, in some cases, from specific waterbody types (e.g , all lakes). Given
the ongoing atmospheric sources of mercury and the long-term presence of mercury
in the environment, the most effective way to protect public health for the next few
decades will be issuing fish consumption advisories to ensure the public knows what
level of fish from specific waters is safe to eat

How is the methylmercury criterion derived?

To assess health risks, EPA developed a reference dose that is a scientifically
justifiable maximum level of exposure to protect public health from all toxic effects
EPA based the methylmercury criterion on a new reference dose that protects all
exposed populations. EPA also updated the exposure assessment and relative source
contribution following the recently published 2000 Human Health Methodology The
resulting criterion of 0 3 mg methylmercury/kg in fish tissue should not be exceeded
to protect the health of consumers of noncommercial freshwater/estuarine fish EPA

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has taken into account the fact that consumers of freshwater/estuarine fish are also
consumers of marine fish

EPA suggests three approaches that can be used to translate fish tissue
methylmercury concentrations into concentrations of methylmercury found in the
water column:

© Calculate site-specific bioaccumulation factors based on data collected from a
specific waterbody,

© Calculate site-specific bioaccumulation factors based on computer models, and

© Use experimentally-derived bioaccumulation factors that are based on field
data published in the criteria.

EPA developed a set of empirically- derived bioaccumulation factors in the initial
efforts to derive a revised ambient water quality criteria for methylmercury EPA has
also derived factors to translate methylmercury in water to its total mercury
equivalent.

How can this criterion help control mercury pollution?

The United States needs to establish effective source control and management
programs in the coming years to begin to recover from the widespread mercury
contamination in our aquatic environments Such actions will hopefully reduce
mercury contamination so that fish consumption advisories can be removed. EPA
expects the criterion recommendation to be used as a guide by States, authorized
Tribes, and EPA in establishing or updating water quality standards that may serve

as a basis for pollutant source control and for fish and shellfish consumption
advisories.

What future activities are related to this criterion?

EPA recognizes and emphasizes that States and authorized Tribes will need
additional specific procedures and water quality program guidance to implement the
water quality criteria they adopt based on this guidance. These procedures include,
but are not limited to, procedures for translating methylmercury concentrations in
fish to total mercury concentrations in ambient surface water or effluent, and
procedures for setting permit limits and calculating Total Maximum Daily Loads

EPA is developing these procedures and guidance documents for this water quality
criterion.

How do I obtain a copy of the criteria document?

You can get copies of the criterion document titled Water Quality Criterion for the
Protection of Human Health: Methylmercury from EPA’s National Service Center
for Environmental Publications (NSCEP) by calling 1-800-490-9198. Or you can get
the document and related fact sheet from EPA’s web site at

http://www.epa gov/waterscience/standards/methylmercury/ .

Where can I get more information?

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